Tails

Not to be confused with the tail texture, which most of the animals have including the Mouse.

The Tails of an animal is an important body part, due to its vulnerability. It is recommended for all animals, even the largest ones, to keep their tails well-guarded, for the reasons below. Every animal except the Mouse, Shrimp, Chipmunk, Trout and Crab should watch their tails, these exceptions being due to said animals not having tails vulnerable to a tail-bite.

Tail-biting

Tail-Biting is a game mechanic that allows a prey animal to fight back by biting the tail of a predator. If a tail is bite-able, it will be highlighted with a light green outline. The only animals without a bite-able tail are the Rabbit, Trout. Arctic Hare, Mouse, Shrimp, Chipmunk, Lemming, Snail, and Crab. Animals that are neutral (with a dark green outline) cannot have their tails bitten, unless they are tier 15 or above.

When it occurs - although uncommon if a predator is at least somewhat aware of their surroundings - it counts as one bite and the prey gets 40 XP + 2% of the bitten animal's XP, said to be with a maximum of double the biter's current XP, even though there really is no maximum.

For example, assume a Rabbit that has 200 XP bites a Zebra that is less than 2K XP away from reaching Cheetah. When the rabbit bites it, the Zebra loses 400 XP(40+360(18000*0.02)), and the Rabbit immediately becomes a Fox, because it has 600 XP. The fox cannot bite tails for 3 seconds, due to upgrade invulnerability. If it were to bite 2 more times, then it would gain about 750 XP. Then, if it bites one more time, it immediately becomes a Zebra, about 1K away from Cheetah. A common strategy is for a small animal to wait until a predator is busy with other large creatures, then tail-bite it and run, gaining enormous amounts of XP for it's size.

A unique message occurs when the player is killed by a tail-bite

Trivia

Some animals appear to have huge tails, but only a small part can be bitten. The longest tail is the Blue Whale’s, and one of the shortest tails is the Jellyfish's (with no visible tail at all).

Tails were added on the October 18th update, which has been dubbed by the developer as the 'Tails Update'.

Before this, animals had absolutely no way of defending themselves against a predator, other than abilities and running.